Biomedical Engineering Reference
In-Depth Information
Chapter 10
ARF-Like (ARL) Proteins
Richard A. Kahn, Michael P. East, and Joshua W. Francis
Abstract The ARF-like (ARL) proteins, within the ARF family, are a collection of
functionally diverse GTPases that share extensive (
40 %) identity with the ARFs
and each other and are assumed to share basic mechanisms of regulation and a very
incompletely documented degree of overlapping regulators. At least four ARLs were
already present in the last eukaryotic common ancestor, along with one ARF, and
these have been expanded to
>
20 members in mammals. We know little about the
majority of these proteins so our review will focus on those about which the most is
known, including ARL1, ARL2, ARL3, ARL4s, ARL6, ARL13s, and ARFRP1.
From this fragmentary information we extract some generalizations and conclusions
regarding the sources and extent of specificity and functions of the ARLs.
>
Keywords ADP-ribosylation factor-like (ARL) • ARL1 • ARL2 • ARFRP1
• ARL13B • ARL GAP • ARL3 • ARL4 • ARL6
10.1
Introduction
A review of the ARL proteins today really requires one to review the ARF family as
a whole and reflect upon the functions and mechanisms that are shared between the
ARFs and ARLs and perhaps highlight those that are not. Because we are
discussing a gene family we assume a common origin and functionality, with
paralogs diverging in sequence and increasingly in functions, with time. Phyloge-
netic analyses revealed the presence of at least six members of the ARF family in
the last eukaryotic common ancestor: ARF, ARL1, ARL2, ARL8, ARFRP1, and
SAR1 (Li et al.
2004
). Preliminary phylogenetic data coming from a greatly
expanded set of proteomes suggest that this is likely an underestimate (M. Elias,
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